Optoelectronic device

ABSTRACT

An optoelectronic device includes a substrate ( 6, 7 ) comprising semiconducting material and an array of smart pixels arranged on or in the substrate, each smart pixel comprising at least one layer ( 12 ) of organic light emitting material, and a light permeable electrode ( 13 ) in contact with the organic layer on a side thereof remote from the substrate. The smart pixels may be capable of one or more of a range of functions, including image sensing, processing, communication and display.

BACKGROUND TO THE INVENTION

[0001] The present invention relates to an optoelectronic device.

[0002] Organic light emitting diodes (OLEDs) comprise certain organicmaterials which are known to emit light under electrical stimulation.The materials can be either small molecules or polymer materials (inpolymer light emitting diodes, PLEDs). These materials require differentprocesses for practical manufacture into devices. Small moleculematerials are deposited onto a substrate by vapour deposition whilstpolymers are cast onto a substrate from a solution by spin-coating,printing, doctor blading or a reel-to-reel process. In a typical polymerLED, a polymer layer is deposited, by spin coating, onto indium tinoxide (ITO) coated glass. This is followed by heat treatment to driveoff residual solvent and a reflective metal electrode is then evaporatedonto the top surface of the polymer layer. The ITO, which istransparent, forms the other electrode and the polymer emits lightthrough the ITO coated glass when a voltage is applied between theelectrodes. Current and voltage control of the light emission is known.

[0003] Both types of materials and processes have been used to fabricatearrays on a number of different transparent and non-transparentsurfaces. Methods known in the art for creating full colour displaysinclude ink-jet printing of polymer solutions and vapour deposition ofsmall molecule materials. Other known methods include the use ofmonochrome displays fitted with individual absorptive filters or colourchanging media filters. Whilst both materials appear compatible withphoto-resist technology, in practice the processing has reduced theefficiency and lifetime of the devices to unacceptable levels.High-resolution colour and monochrome displays have been demonstratedfor small molecules by depositing them into microcavities. InEP-0,774,787, a full colour OLED array is fabricated on a CMOS substrateby this method. The drivers for the diode array are formed in thesubstrate.

[0004] Various types of liquid crystal display have been fabricated oncrystalline silicon (LCOS) and other silicon materials such aspolysilicon on glass. The silicon material provides the active matrixdrive circuitry as well as the substrate. Similarly, a vacuumfluorescent display has been fabricated on crystalline silicon.

[0005] The manufacture of arrays of OLEDs on non-transparent substratessuch as CMOS or bi-CMOS is hindered by the need to fabricate an (atleast semi-) transparent electrode on top of the organic layers to allowlight emission and viewing. Deposition of indium tin oxide directly ontothe organic layers can cause unacceptable deterioration in the deviceperformance. Another consideration is the need to carefully select thechoice of metal electrode material directly in contact with thesubstrate so that it is fully compatible with microelectronicmanufacturing equipment.

[0006] An electronic display is, in effect, a pixelated optoelectronicdevice in which electronic information is fed on to the display andconverted to optical information on a pixel-by-pixel basis. A smartpixel array (SPA) is an array of optoelectronic pixels (also calledcells or units) in which each pixel has the capability to communicatewith other pixels in the same array or another array by electricaland/or optical means. The configuration of the communication (whichcells communicated with which others by which means and in whichdirection) is usually dynamically programmable by means of optical orelectrical signals fed to the SPA. Often communication within an arrayof pixels on the same substrate is done by electronic means whilecommunication between pixels in separate arrays or on separate or remotesubstrates is done by optical means.

[0007] SPAs have been implemented in the past in technologies such as,for example, liquid crystal over crystalline silicon, monolithic III/Vsemiconductor, and III/V semiconductor bonded to CMOS silicon byflip-chip technology.

[0008] SPAs have been used in fields as diverse as, for example, imageprocessing, telecommunications switching and optoelectronic neuralnetworks.

[0009] The optical communication between SPAs is often carried out usinglight or electromagnetic radiation of wavelengths other rather thanvisible. For example, SPAs used in telecommunications systems often useinfra-red wavelengths.

SUMMARY OF THE INVENTION

[0010] According to the present invention there is provided anoptoelectronic device including a substrate comprising semiconductingmaterial and an array of smart pixels arranged on or in the substrate,each smart pixel comprising at least one layer of organic light emittingmaterial, and an (at least semi-) transparent electrode in contact withthe organic layer on a side thereof remote from the substrate.

[0011] Preferably, and in particular where the device forms a display,the electrode comprises an electrically conducting polymer, andpreferably, the surface of the substrate is polished or smoothed toproduce a flat surface.

[0012] The substrate may consist of amorphous, polycrystalline ormonocrystalline silicon. Alternatively, the substrate may comprise alayer of amorphous, polycrystalline or monocrystalline silicon overlyinga layer of glass or sapphire. Preferably, the polishing or smoothing ofthe substrate is effected prior to the deposition of the electrode, ororganic, materials of each OLED smart pixel. The smart pixels of thearray may be different, similar or identical, or the array may compriseany two or all three of different, similar and identical smart pixels.Pixels in the array which are physically similar or identical may beprogrammed once and for all or dynamically to perform the same ordifferent functions.

[0013] The smart pixels are preferably of the same size and may bearranged as squares or rectangles on a Cartesian grid. Other grids, suchas hexagonal pixels on a hexagonal grid or ring, and wedge shaped pixelson a polar or radial grid, are also feasible as embodiments of theinvention.

[0014] Each smart pixel of the array is capable of carrying out one,some or all of the following tasks:

[0015] Process information electronically within the pixel

[0016] Store information within the pixel

[0017] Transmit electrical signals to one or more other pixels in thesame array by means of conducting layers which form part of an activecircuit or to one or more pixels in one or more other arrays by a meansconventionally used in electric or optical chip to chip interconnect(such as copper tracks on a PCB, wires in a ribbon cable or opticalfibres)

[0018] Receive electrical signals from one or more other pixels in thesame array by means of conducting layers which form part of an activecircuit or to one or more pixels in one or more other arrays by a meansconventionally used in electric or optical chip to chip interconnect(such as copper tracks on a PCB, wires in a ribbon cable or opticalfibres)

[0019] Transmit optical signals to one or more other pixels in the samearray or another array by means of light waves propagating in free spaceor through an optical system

[0020] In the case of organic light emitters, such as LEDs, micro-cavityLEDs, laser diodes or organic modulators utilising absorption shiftingmechanisms, convert electrical signals into optical signals, foroff-chip communication

[0021] Receive optical signals from one or more other pixels in the samearray or another array by means of light waves propagating in free spaceor through an optical system

[0022] The above processes may be carried out singly, or some or alltogether at the same time, or in sequence, one after the other or in anyother combination.

[0023] Optical signals received by a pixel may be arranged to beconverted into electrical signals by conversion means, for example, oneof the following:

[0024] One or more PN junction diodes or PIN diodes or phototransistorsor photoconductors or one or more other photosensitive elements or somecombination of these, within the active substrate, (each) electricallyconnected to suitable amplification circuits within the active circuit

[0025] One or more organic photodiodes or phototransistors or otherphotosensitive elements formed in a layer above the active circuit and(each) electrically connected to the input of a suitable amplificationcircuit within the active circuit

[0026] Some combination of the above semiconductor photosensitive andorganic photosensitive structures each of which is electricallyconnected to the input of a suitable amplification circuit within theactive circuit

[0027] Electrical signals within the pixel are preferably arranged to beconverted into optical signals by means of one or more driver circuits,within the active circuit, (each of) whose output is connected to theunderside of an arrangement of one or more organic light emitting diodesin series or parallel or both, formed in a layer above the activecircuit. The top side of the organic light emitting diode or diodes ispreferably connected to an electrode which is common to some or all ofthe organic light emitting diodes in the smart pixel array. This commonelectrode is preferably of metal and in contact with the substrate.Depending on the relative work functions of the metal and transparentelectrodes, either may serve as the anode with the other constitutingthe cathode.

[0028] In one embodiment, the smart pixels are configured to form anoptoelectronic communication link on- and off-chip, for microsystemintegration, computer interconnect, datacom or telecom applications. Forexample, the smart pixels can enable chip-to-chip communication torelieve data bottlenecks, enable optical clock distribution tosynchronise systems or allow direct chip access to optical disks oroptical memories where conversion to/from electrical signals isperformed at the smart pixel.

[0029] The pixel configuration may be capable of providing databuffering and multiplexing and demultiplexing functions and handlingdata protocols. Organic photodiodes or phototransistors may convertoptical signals into electrical signals for on-chip communication.Parallel communication links can be provided by spatial, temporal orwavelength multiplexing. Wavelength multiplexing can be provided bydifferent pixels preferentially emitting and/or absorbing differentcolours of light. For example, microcavity structures, possibly inconjunction with doping of rare-earth metals, can be employed to givenarrow-band sources at selected wavelengths. The doping,microstructuring, or voltage applied can be selected to varying thewavelength from pixel to pixel as required. Also, organic emittingdevices, in conjunction with narrow band photoluminescent, colourconversion structures can be employed.

[0030] The optoelectronic communication links can be point-to-point,multi-cast or broadcast. The links can be static (fixed) or dynamic(reconfigurable). Optical fibres, optical waveguides or free-spacemicrooptics/optics can be used to transfer the light from source todestination. The organic optoelectronic devices can be micro-structuredto ease optical coupling. Passive or active optical waveguide structuresin organic or inorganic materials can be integrated with the smartpixels on the same substrate.

[0031] In one embodiment, the smart pixels are configured as an imagesensor and/or display. Broadband or narrowband light in the range ofwavelengths from the ultraviolet to infrared, incident upon the smartpixels can be converted to a digital representation and stored at thepixels. Localised image-processing operations, such as imageenhancement, equalisation or data encryption can be performed. The datacan then be output optically in the form of a displayed image, ortransported elsewhere as optical or electrical communication signals.For example, infra red images can be converted for display in visiblecolours.

[0032] In one embodiment, the smart pixels are configured as an imagesensor and/or printer. The optical signals can be used to transferimages from storage on the pixel array to a light sensitive film.

[0033] The organic light emitting material is preferably a polymer butmay alternatively be a monomer or a transition metal chelate. Apart fromthe light emitting material, organic layers in the pixel elements mayinclude an electron transport material layer, a hole transport materiallayer, a protective cap material layer and a conducting polymer materiallayer.

[0034] As well as a conducting polymer, the (at least semi-) transparentelectrode may comprise further layers, e.g. of indium tin oxide (ITO) orother transparent or semitransparent metal oxides or low or high workfunction metals, or conducting epoxy resin, deposited onto the organiclayer furthest from the substrate. Alternatively, a glass or plasticsheet, coated with ITO, conducting polymer, or at least one of thelayers that constitute the (at least semi-) transparent electrode, maybe bonded to said furthest layer or another layer of this electrode, tocomplete the electrode and serve as a barrier to the ingress of oxygenand water. The surface of the device may be completed by encapsulationwith a further layer of polymer or glass.

[0035] The preferred conducting polymer is poly(ethlyendioxythiophene),sold by Bayer AG under the trade mark PEDOT. Other molecularly alteredpoly(thiophenes) are also conducting and could be used, as could theemaraldine salt form of polyaniline. To improve the adherence of PEDOTto certain smooth substrates a polymer blend with a non-conductingpolymer, preferably poly (vinyl alcohol) (PVA), can be made. Forexample, a 9 wt % solution of PVA with PEDOT in a 10(PVA):6 volume ratiocan be used. A wide range of molecular weights of PVA can be usedwithout much difference in the resultant film or its conductivity.

[0036] In still another embodiment, a metal electrode may consist of aplurality of metal layers, for example a higher work function metal suchas aluminium deposited on the substrate and a lower work function metalsuch as calcium deposited on the higher work function metal. In anotherexample, a further layer of conducting polymer lies on top of a stablemetal such as aluminium. Preferably, the electrode also acts as a mirrorbehind each pixel and is either deposited on, or sunk into, theplanarised surface of the substrate. However, there may alternatively bea light absorbing black layer or reflective structure between eachpixel.

[0037] High work function metals that could be used include tungsten,nickel, cobalt, platinum, palladium and their alloys, and possiblyniobium, selenium, gold, chromium, tantalum, hafnium, technetium andtheir alloys.

[0038] The substrate may also provide data drivers, data converters andscan drivers for processing information to address the array of pixelsso as to create images.

[0039] In a method of making the optoelectronic device according to theinvention, the organic devices can be integrated directly onto thesemiconductor circuit substrate, formed by vacuum deposition, printing,stencilling or spin coating methods, or formed separately andhybridised, using flip-chip or wafer bonding methods. These processescould be low-temperature (<100° C.) and allow full hermeticencapsulation, to maximise device life-time and performance.

[0040] In still another embodiment of the method, selective regions of abottom conducting polymer layer are made non-conducting by exposure to asuitable aqueous solution allowing formation of arrays of conductingpixel pads which serve as the bottom contacts of the pixel electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order that the present invention may be more readilyunderstood, reference will now be made, by way of example only, to theaccompanying drawings, in which:—

[0042]FIG. 1 is a schematic diagram of a smart pixel which can beimplemented using the invention;

[0043]FIG. 2 is a schematic cross section of a smart pixel according toan embodiment of the invention;

[0044]FIG. 3 is a schematic cross section of a single pixel of aplanarised substrate according to an embodiment of the invention (notshowing the polymer LED);

[0045]FIG. 4 is a schematic cross section of an alternative substrate,showing the deposited polymer LED, and

[0046]FIG. 5 is a schematic, fragmentary side view of an array ofpolymer LEDs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047]FIG. 1 shows a smart pixel which is capable of receiving opticalsignals at an optical Rx 1 and electrical signals at an electrical Rx 2.The received signals are processed in a processor 3 where data canoptionally be stored. Optical signals are transmitted from an optical Rx4 and electrical signals are transmitted from an electrical Tx 5.

[0048] Each smart pixel in the array of the invention may be asexemplified in FIG. 2. The pixel comprises, from bottom to top, thefollowing elements: a passive substrate 6, an active substrate 7, activeelectronic devices 8, circuit electrical interconnections 9, padconnections 10 to organic conducting and light emitting/detectinglayers, two unspecified series 11, 12 of conducting, organic conducting,hole transport, electron transport and organic light emitting ordetecting layers, and a transparent conducting layer 13 forming atransparent electrode. One of the series 11 includes at least one lightdetecting layer whilst the other series 12 includes at least one lightemitting layer. A planarising dielectric 14 may cover the activesubstrate 7.

[0049] Once the active matrix circuitry has been fabricated in thesemiconductor substrate, for example using CMOS technology, the surfaceof the substrate can be planarised. This planarisation either takesplace as part of the manufacturing process of the integrated circuit oras a subsequent customising step.

[0050] As shown in FIG. 3, the planarisation is effected by depositingthe dielectric 14, for example a polymeric material, on the surface ofthe active substrate 7. A conducting polymer that can be patterned tocreate areas of insulation can be used instead for this purpose. A metalmirror/electrode 34, which may be of aluminium, for connecting one ofthe series of layers 11 to the appropriate point in the circuit, is thendeposited, the connection to the circuit being established by a metallicconducting via 36. Metallised portions of the CMOS circuit aredesignated 38.

[0051]FIG. 4 shows an alternative arrangement in which theelectrode/mirror 34 is sunk into the dielectric surface, i.e. fullplanarisation is achieved.

[0052]FIG. 4 also shows one way in which the device construction can becompleted. The series of layers 11 is deposited and the display issealed by coating with a glass plate 42 coated on its inner surface witha transparent conducting layer 43 which comprises the conducting polymerand, optionally, ITO.

[0053]FIG. 5 shows an alternative device construction including aparticular example of the series of deposited layers. For simplicity,FIG. 5 shows ordinary pixels instead of smart pixels, but the example isequally applicable to forming smart pixels according to the invention.On the substrate 32 there are deposited, in turn, the planarisedaluminium electrode/mirror 34, optionally an electron or hole transportlayer 44, a light emitting polymer 46, and a transparent electrode 48.The transparent electrode may for example consist of a thin layer ofhigh work function metal 49, of a thickness to be adequatelytransparent, a layer of conducting polymer 50 and a layer of ITO 51. Anencapsulation layer/barrier 52 which seals all of the LEDs of the array,including their sides, completes this example of the displayconstruction, three pixels of which are shown in FIG. 5.

[0054] In manufacturing the display shown in FIG. 5, the flat metalmirrors 34 are applied to the surface of the substrate 32 (preferably aCMOS or bi-CMOS backplane) so as to cover most of the area of each pixelwith minimal gaps between the mirrors. Chemical Mechanical Polishing maybe used to enhance the global and local planarisation.

[0055] The layers of polymer and related materials can be deposited byan automated technique using equipment currently used for applyingphoto-resists used for the patterning of integrated circuit layers. Thisgives precise control and a uniform thickness for each layer.Alternatively, the polymer layers could be ink-jet printed. Rare earthchelates can be vacuum deposited.

[0056] The encapsulation layer 52 is applied after making theconnections to the transparent electrode in each pixel. Encapsulation,and possibly the assembly of the pixel, are carried out in clean, dryconditions under a partial vacuum, or a suitable inert or controlledatmosphere.

[0057] The display of the invention is robust, the organic LEDs beingwell protected, but has simplified manufacture and encapsulation. Thepower generated as heat should be manageable but could be decreased byreducing the current or voltage used to drive each element. If currentrouting problems arise, multiple power supply bond pads can be used onthe silicon chip.

INDUSTRIAL APPLICABILITY

[0058] Devices according to the present invention can be used toimplement any of the following:

[0059] Optoelectronic displays

[0060] Optoelectronic computing systems, including neural networks anddigital parallel networks

[0061] Optoelectronic interfaces between the electrical/electronicdomain and the optical domain in datacoms/telecoms, optical backplanesand chip-to-chip (inter and intra) interconnect

[0062] Optoelectronic cross-connects, switches, buffers, add/dropmultiplexers, for datacoms/telecoms, optical backplanes and computinginterconnects

[0063] Smart sensors and/or printers for digital photography,photolithography and material processing

[0064] Smart sensors and/or displays, with integrated functions such aspattern recognition, compressed data, image enhancement, smartresolution, smart gain, smart colour conversion.

[0065] All forms of the verb “to comprise” in this specification mean“to consist of or include”.

1. An optoelectronic device comprising a substrate providing activecircuitry, and an array of smart pixels, each smart pixel comprisingpart of said active circuitry as well as at least one organic layerwhich performs at least one of the functions of light detection, lightemission, light modulation and light amplification.
 2. A deviceaccording to claim 1, wherein the substrate comprises a semiconductinglayer.
 3. A device according to claim 2, wherein the substrate comprisesa layer of silicon.
 4. A device according to claim 3, wherein said layerof silicon overlies a layer of insulating material.
 5. A deviceaccording to any preceding claim, wherein the surface of the substrateis smoothed or polished to produce a flat surface.
 6. A device accordingto any preceding claim, wherein the array comprises smart pixels capableof processing information electronically within the pixel.
 7. A deviceaccording to any preceding claim, wherein the array comprises smartpixels capable of storing information within the pixel.
 8. A deviceaccording to any preceding claim, comprising electrical means via whichsmart pixels of the array are arranged to transmit and/or receiveinformation to or from one or more other pixels.
 9. A device accordingto any preceding claim, comprising optical means via which smart pixelsof the array are arranged to transmit and/or receive information to oneor more other pixels.
 10. A device according to claim 8 or 9, whereinsaid one or more other pixels are in another array.
 11. A deviceaccording to any preceding claim, wherein the array comprises smartpixels comprising conversion means capable of converting optical signalsinto electrical signals.
 12. A device according to claim 11, whereinsaid conversion means comprise at least one of a PN junction diode, aPIN diode, a phototransistor and a photoconductor.
 13. A deviceaccording to claim 11 or 12, wherein said conversion means are in theactive circuitry.
 14. A device according to claim 11 or 12, wherein theconversion means comprise at least one organic layer formed over thesubstrate.
 15. A device according to any preceding claim, wherein thearray comprises smart pixels capable of converting electrical signalsinto optical signals.
 16. A device according to claim 15, wherein saidsmart pixels capable of converting electrical signals into opticalsignals are connected to an arrangement of organic light emitting diodesformed in a layer over the substrate.
 17. A device according to claim15, wherein said smart pixels capable of converting electrical signalsinto optical signals are connected to an arrangement of organic lightmodulators or amplifiers formed in a layer over the substrate.
 18. Adevice according to any preceding claim, wherein the array comprisessmart pixels capable of modifying or amplifying light under the controlof electrical signals.
 19. A device according to any preceding claim,wherein at least one of the active circuit parts of the smart pixels isarranged to provide a function selected from data buffering,multiplexing, demultiplexing and the handling of data protocols.
 20. Adevice according to any preceding claim, comprising parallelcommunication links provided by one of spatial, temporal and wavelengthmultiplexing.
 21. A device according to claim 20, wherein differentpixels preferentially emit and/or absorb different colours of light soas to provide wavelength multiplexing.
 22. A device according to claim21, comprising microcavity pixel structures providing narrowband sourcesat selected wavelengths.
 23. A device according to claim 22, whereinsaid structures are doped differently to vary the wavelength from pixelto pixel.
 24. A device according to claim 23, comprising narrowbandphotoluminescent colour conversion pixel structures.
 25. A deviceaccording to any preceding claim, comprising point-to-pointoptoelectronic communication links.
 26. A device according to any one ofclaims 1 to 24, comprising multi-cast optoelectronic communicationlinks.
 27. A device according to any one of claims 1 to 24, comprisingbroadcast optoelectronic communication links.
 28. A device according toclaim 25, 26 or 27, wherein said optoelectronic communication links arereconfigurable.
 29. A device according to one of claims 25 to 28,comprising optical waveguide structures integrated with the smart pixelson the same substrate.
 30. A device according to any preceding claim,wherein the smart pixels are configured as an intelligent image sensor.31. A device according to claim 30, wherein the smart pixels arearranged to convert light incident thereon to a digital representationand to store the representation.
 32. A device according to any precedingclaim, wherein smart pixels are arranged to perform localised imageprocessing operations, such as image enhancement, equalisation or dataencryption.
 33. A device according to any preceding claim, wherein thesmart pixels are configured as an intelligent image display.
 34. Adevice according to any preceding claim, wherein the smart pixels areconfigured as a printer, optical signals being used to transfer imagesfrom storage on the pixel array to a light sensitive film.
 35. A deviceaccording to any preceding claim, wherein the organic layer comprises apolymer.
 36. A device according to any preceding claim, wherein theorganic layer comprises a monomer.
 37. A device according to anypreceding claim, wherein the organic layer comprises a transition metalchelate.
 38. A device according to any preceding claim, wherein thesmart pixels comprise at least one further layer, selected from anelectron transport material layer, a hole transport material layer, aprotective cap material layer and a conducting polymer material layer.39. A device according to any preceding claim, comprising a lightpermeable electrode in contact with the organic layer.
 40. A deviceaccording to claim 40, wherein the light permeable electrode is on aside of the organic layer remote from the substrate.
 41. A deviceaccording to claim 40, wherein the light permeable electrode comprises aconducting polymer.
 42. A device according to claim 41, wherein theconducting polymer is a molecularly altered poly(thiophene).
 43. Adevice according to claim 42, wherein the conducting polymer ispoly(ethlyendioxythiophene).
 44. A device according to claim 43, whereinthe poly(ethlyendioxythiophene) is blended with poly (vinyl alcohol).45. A device according to claim 41, 42, 43 or 44, wherein the lightpermeable electrode comprises a further layer, selected from indium tinoxide, another light permeable metal or metal oxide, and conductingepoxy resin, on the organic layer of the pixel that is furthest from thesubstrate.
 46. A device according to any preceding claim, comprising atleast one organic encapsulation layer on the surface of the device. 47.A device according to any preceding claim, comprising at least oneorganic encapsulation layer on the surface of the device.
 48. A deviceaccording to any preceding claim, including an electrode, formed from ahigher work function, light permeable, conducting material, selectedfrom aluminium, tungsten, nickel, cobalt, platinum, palladium, niobium,selenium, gold, chromium, tantalum, hafnium, technetium and theiralloys, and indium tin oxide, deposited on the substrate.
 49. A deviceaccording to any one of claims 1 to 47, including a stable metalelectrode having a layer of conducting polymer overlying the stablemetal.
 50. A device according to claim 48 or 49, wherein the electrodeis arranged to act as a mirror behind each pixel.
 51. A device accordingto any preceding claim, wherein the substrate comprises circuitry forprocessing information to address the array of pixels so as to createimages.
 52. A method of making an optoelectronic device including asubstrate comprising semiconducting material and an array of smartpixels arranged on or in the substrate, each smart pixel comprising atleast one layer of organic light emitting material, and a lightpermeable electrode in contact with the organic layer on a side thereofremote from the substrate, wherein the organic layers are integrateddirectly onto the substrate.
 53. A method of making an optoelectronicdevice including a substrate comprising semiconducting material and anarray of smart pixels arranged on or in the substrate, each smart pixelcomprising at least one layer of organic light emitting material, and alight permeable electrode in contact with the organic layer on a sidethereof remote from the substrate, wherein the organic layers are formedseparately and hybridised.
 54. A method of making an optoelectronicdevice including a substrate comprising semiconducting material and anarray of smart pixels arranged on or in the substrate, each smart pixelcomprising at least one layer of organic light emitting material, and alight permeable electrode in contact with the organic layer on a sidethereof remote from the substrate, wherein selective regions of a bottomconducting polymer layer are made non-conducting by exposure to asuitable aqueous solution allowing formation of an array of conductingpixel pads which serve as the bottom contacts of the light permeablepixel electrodes.
 55. A method according to claim 52, 53 or 54, whereina glass or plastics sheet, coated with one of indium tin oxide,conducting polymer, and at least one layer of a light permeableelectrode, is bonded to the organic layer of the pixel that is furthestfrom the substrate or to another layer of this electrode, to serve as abarrier to the ingress of oxygen and water.